Officials running the UN's oil-for-food programme for Iraq were guilty of widespread mismanagement, according to documents newly released.
The programme was supposed to soften the burden on Iraqis
An independent inquiry into corruption in the $60bn programme has published dozens of reports by UN auditors.
They find inadequate monitoring of the programme and of contractors hired to inspect the flow of oil and goods.
However, the reports do not find evidence of any irregular activities or corruption among UN staff themselves.
The independent commission was set up after US congressional allegations of multi-billion dollar corruption.
The reports compiled by the UN's Office of International Oversight Services identify continuing lapses in supervision.
Contractors are accused of overcharging the programme by hundreds of thousands of dollars for hours that were not actually worked.
The investigating panel said auditors did not properly check oil purchase and humanitarian aid contracts. Had they done so, they could have limited the Iraqi government's ability to generate income by violating UN sanctions.
The reports were released by Paul Volcker, the former chairman of the US Federal Reserve, who was asked by UN Secretary General Kofi Annan to investigate the oil-for-food programme.
The BBC's Susannah Price, at the UN in New York, says the report raises serious issues concerning the operation of the programme, which was meant to bring relief to ordinary Iraqis suffering under sanctions.
Separate inquiries in the US Senate have been told that Saddam Hussein's regime made more than $21bn from illicit oil sales and kickbacks through the UN programme.
The CIA website has published a list of people it said the Iraqi regime tried to bribe. It includes senior foreign politicians and Benon Sevan, the former head of the oil-for-food programme.
Mr Sevan has firmly denied doing anything wrong.
Mr Volcker is expected to issue a preliminary report at the end of January and to finish his investigation in June.